Telephone system



Feb. 12, 1935.` J. B. NEwsoM TELEPHONE SYSTEM Filed Dec. 20, 1932 i /N VEA/TOR J.B .NEWSOM Feb. 12, 1935.` J B NEWS'QM 1,991,170

TELEPHONE SYSTEM Filed Dec. 2o, 1952 9 sheets-sheet' 2 a i N lli-ll' /ITH no 74m/ STEP /NVENTOR J. B.NEW$0M BVWWM A TTORNEY J. B. NEWSOM TELEPHONE SYSTEM Feb. 12, 193s,

Filed Dc.

20, 1952 9 Sheets-Sheet 3 Fllnlmm ATTORNEY Feb.12,1935. BNEWSOM A 1,991,170

TELEPHONE SYSTEM Filed Dec. 20, 1952 9 Sheets-Sheet 4 /lT/-l ROTARY STEP BVMW/MVM A TTORNEV Feb. 12, 1935. J, B NEWSOM I 1,991,179

TELEPHONE SYSTEM Filed DGO. 20, 1932 9 Sheets-Sheet 5 rm om SUS /NVENTOR J. 5 NEWSOM jay A TTORNEV Feb. 12, 1935.

. J. B. NEwsoM A TELEPHONE sYsTEM Filed Dec. 20, 1932 QSheets-Sheet 6 v @v1 N8. Bvl.

/NvE/vroe J. B .NEWSOM BV WBN Feb. 12, 1935. J, B NEwsoM 1,991,170

TELEPHONE SYSTEM l Filed DGS. 20, 1932 9 Sheets-Sheet 7 TH. ROTA/ey STEP /NVENTOR J. B NE WSOM A TmRA/EV Feb- 12, 1935; J. B. NEwsoM' 1,991,170

TELEPHONE SYSTEM Filed Deo. 2o. 1932 9 sheets-sheet s wil, n i 'n I N A TTOR/VEV J. B. NEWSOM TELEPHONE SYSTEM Feb. 12, 1935.

Filed Des. 2o, 1952 T9 sheets-sheet x U m21 mm3 u, 1M r i n 1- V hof I rolw Lum IIN. 1 ,Jb j? www mmm Mwmo ....w tu mmm NB @GE Patentes Pesiz, 1935 i 1,991,170

UNITEDsTATEs'PATENToFFics f James B. Newsom,` Great Neck, N.\Y`., assignor to Bell Telephone Laboratories, Incorporated, New t I Y York, N. Y., a corporation of New York n i Application December 20, 1932 Serial No. 648,077 Y s claims. (Crim-27,),`

This invention relates to telephone systems and current ,over either conductor since ringing cure more particularly to vtraffic intercepting equip- `rent or direct current may be received over either ment for use in automatictelephone systems. `conductorr if the call is intercepted at a connector The object of the invention is to provide an imrlor fromV a plugging-up line and directV current proved arrangement `for extending intercepted may be received over the ring conductor if the 5 calls to a centralized Aswitchboardi j call is intercepted atalocal or toll selector. Means` In automatic telephone systems it is usual to i arealso provided,` for reversing the line conducconnect an intercepting trunk to blank terminals tors from the trunk finder in case ringingcurinthe selector `and connector banks andalso to ient `iS i'eeeved CVel JElle 'Dip' COndilCtOPn QI'CleI' 1o provide an intercepting trunk from a pluggngeup that the trippingresistance may `always be con- 1o line for intercepting callsto a subscriberwhose nectedto the conductor over which the ringing line is temporarily remo-ved from service. WhenV t current is received and in order to maintain the e the intercepting operators positions are located same supervisory conditions as exist when sig-` in the same oce asthat in which the callsr are naling current is received over the ring conductor.

l5 intercepted, the intercepting trunks terminatein o The invent/i011 Will be better UndelStOOd by 00nl t' answering jacks at the various positions andin sideringa telephone system in which its features response vto their seizure light correspondinganhave been embodied, suchla system being Shelli/I1 Y swering lamps associated therewith;` When one l schematically in thedrawings which formY a part centralized intercepting A switchboard-is pro- `of ,this specification. The use of the invention 2o vided for several offices each intercepted call is isv not limited, however, to the particular system 20v extended over one of a group 'of trunks to the illustrated and other applications of the'invencentralized A switohbcard, one such arrange` tion will readilyoccur to one skilled in the art.

`ment being disclosed in thepatent to John Wicks, Referring t0 the drawings! t l No. 1,576,884, March 16,1926.

Fig, 1 represents schematicallya tollline L;

in an oflice, irrespective of the pointeat which ment OP andV an outgoing trunk Cirelli T they are intercepted, are concentrated for their fonuse inextending calls to a distant step-byextension over a common group of integroiiice Step OiiCe;` i

trunks to a centralized intercepting switchboard Fig. 2 SllOWS a tell Seleeiel1 TS inthe Stepby- According to this invention all intercepted calls a toll operators cord circuit CO1 position equip- 25` ro by .providing iinder switches individual to the vstepofliee for use in completing cans incoming V v l interoflice trunks and'having access to all of the frein ai manual Vi011 Office; Y intercepting trunks. Since calls` may be interf Fig. 3 Shows@ tell COnneCiJOI' Cileiiit `TC fOr use cepted at various stages oi completion theinterl in Completing Calls nCOIning frein e; 11011 Cffee; cepting trunks are variously Varranged to start i Fig. 3,05 SnOWS a Drunk Circuit lTl OI nl'felCePt* g5 an idle trunk nder switch in response' to their ingI connections extended to-blankterminals in 35 seizure. If a call is intercepted at a connector or the banks 0f OllSeleC'Ol-S i i i e toll selector, ground connected to the sleeve con- Fig` 3b showsa similar trunk circuit ITZ fOr inductor of the intercepting trunkoperatesa start tereeptine CO'nneCtOnS eXtended "i0 blank Deli relay to cause a trunk-nieder to hunt for the minalsi in the banks oi' tollconnectors;

40 seized trunk; if a call is intercepted at a 'local `Fig. 4 shows anautomatic subscribers station'40 selector, a line relay bridged across the linecon A, a line ndei LFk and a iIfSiJ SeleCOI LS; l ductors of the intercepting trunk operates to Fig. 5 shows aconneetei LC fOi' Cenlplei'fing 1002i start an idle trunk finder; and if 'al call is in- "calls;\; t n y l t Y tercepted from a plugginguup line, a ring-up relay t Fig. 5a shows a trunk circuit ITB for intercept-` connected `in series witha condenser acrossthe .ing Calls eXtended te blank terminale in JShe bil/nkv 45 line conductors operates in response to ringing of local selectors; y

1 current to effect the starting of an idle trunk .A Fig.V 6 ShOWS 2 plugging-up line Ci'CUit Piland iinder.` Upon extensionof a call by a trunk'nder, an nieI'CeD-ting Vtr'unkfcircuit IT5 from the plug- V the associated outgoing trunk responds to ringging-uplinerfor extending calls to an intercepting ing current or direct current if the call is inter-` operator; i Y

`cepted at a connector switch or`from a-piugginga Fig 6a` shows a` trunk circuit IT4 for use in up line and responds to direct current received interceptingvcalls extended to blank terminals in lover one of the conductors of the irltercepting the banks of local connectors; t l

trunk if the callis intercepted at a selector switch. f Fig. 7 shows a ,trunk nder TF having access Means are provided for responding to signaling .tothe intercepting trunks from tollrandtlocal 55 CII selectors, from toll and local connectors and from plugging-up lines;v

The toll eperators ,cord and position circuitsl of Fig. 1 may be similar to those `shown and described in the patentl to R. C. Paine, No. 1,836,549, December 15,1931. he'se'lector and connector switches of Figs. 2, 3, 4 and .5 areof the Well known two-motion step-.by-step type as is "als'o'rthe trunk lnder of Fig. 'l'.A Rete'renceina'y be had to pagers 53 to 65 inclusive, or" the second edition or Automatic Telephony by Smith and Campbell, `published in 1921, for a description in' detail ofthe construction and operation 4of such switches. Y

"heyarious intercepting trunks Vl'lll from lthe banker4 ytoll selector TS, 1'12 from the bank of thetoll/cennector TC, ITS from the bank of local selector LS,VIT l from the bank .of the local con- Vnestor LCV and T5 from the `plugging-up line PL all terminate inthe bank of the trunk -iinder TFand inthe banks of similar trunk ndere, each of which is associated with 'a trunk terminating at thecentralized` ViI-itercepting switchboard. The

operationoithe system to extendintercepted calls to a'fcentralized intercepting operatorsposition will be described first for calls incoming from a ltoll operators position and second'for local calls.

y 'Referring to Fig.' A1, a Vcall incoming over toll line L may be answered .by inserting plug 101 of the cord CCl-into jack 100. The talking key f (not shown) is then operated to extend the -conneet-ion `to the operators position circuit OP. Upon inquiry the operator receives the number ef the called subscriber with Vwhich the calling subscriber-or operator desiredconnection'.- 1f the called subscribers line` terminates in a distant au r tornatic cnice, the plug 103to the cord circuit CCl is i-nsertediin a jack connected to a trunk leading to the desired cnice, such vfor instance as the ack '110.3 The sleeve relay 111 of the outgoing trunk-circuit T is thus operated by the energize.- tion of its lower winding'in series with the supervisor-y lamp 104er the cord circuit-CCVlfthe current being insucient to light the lamp. Upon ,operation -oi Athe Adial Ykey (not shown), a circuit is -c'losed `from battery (not shown) in the -posi- K tion circuit through the upper conductor oi cord C01 andr'plug 103,'u-pper 'spring of jack 110, and through the upper back contact and `winding of relay 112, to ground. 'Relay 112-operates, locks under controlV of the sleeve relay 111, and closes( the dialing` 'circuit tirol-n battery at the back con-f tact of the release magnet 240 of the toll selector TS, through the upper winding of line relay 2011,7upper outer back contact of relay '211, lower back contact -of relay 206, `left rlower winding of repeating 4co'il 250, over the lower-conductor o the interoiice trunk line 120, through thev lower'back 'Contact of relay 117tin the outgoing trunk circuit T, outer lower back contact of relay 113, inner upper fronti-contact of frelay 112, tip

' conductors lof 'jack 110, plug 103 `and cord CC).

tiirougl-ithe interrupter contacts lof the "dial 105,y

back through the ring Yconductors of cord C Cl, plug 103 andV jack 110, lower front contact of relay 112, upper back contact oi relay 113,wind-V ing of polarized relay 114, upperbaok contact of V,relay 117, over the upper conductor of trunk 120, Y

outer upper back contact of relay 206, to ground at the inner upper back contact or" relay 206. Theline relay 201 of the selector TS operates thereby closing `an obvious circuit orenergizing release relay 202. Relay 202 connects ground at. v its upper front contact to conductor 219, causingV the operation of relay 210. The circuit for operfatin'g relay 210 is traced from battery through the winding of relay 210inner upperback contact of relay 211, lowermost back contactof relay 208,

to `the ground on conductor 219.

When the toll operator, dials the r'st digit of Y the called subscribers number the line relay 201 responds to the train of impulses thereby created, The first in the usual and well known manner. release of `relay 201 Ycloses a `circuit from battery through the windingof the vertical stepping inagnet 220, winding of relay 203, upper back contact of relay'21'2, lower front contact of relay 202, to ground at'the backV Contact of relay 201. vertical stepping magnet 220 and relay 203 both operate, the operation oi the magnet-being eiec- 1 tive V.torstep the brushes 215, 216, 217 and 218 up tov the irst level oi the terminal,bank.'v Relay 203 closesha circuit from battery through the winding of `relay 204, inner. front kcontacter @relay i 203, over conductor 219 to ground at relay 202. Relay 204 operates and'it'locks through its inner TheI lower iron-t contact and lowerrnost back contact of relay 212 to the ground-on-'conductor 219. As soon as the shaftland brushes of' the switch move out oi' normalposition, the verticaloff-'nor-V mal springs'VON are actuated, thereby' closing a circuit for `operating'relay 205; this Vcircuit is traced from battery through the back contact of the release magnet 24.0, `upper contacts oi the VON springs, winding of relay 205, outer iront contact oi relay`203 to the ground on conductor 219. Relay 205 locks to` ground at its lett front l Contact, under control of the back contact of the l rotary stepping magnet230, but independent of the continued operation of relay'203. The reoperation of relay 201 at the end of the iirstY im- Cro pulse causes the release ofthernagnet 220. Each succeeding release and reoperation of Yline relay 201 in response to ythe dialingrof'the rst digit of the called subscribers number causes aY corre spondingoperation and release of the magnet 220, thereby steppingy the Vselector brushes 4up to 'the level which corresponds to the digit fdialed. Being slow torelease, relay 203 remains operated until all of t -e rst train of impulses have been received. Relay 202 is alsoslow to release and remains operated rduring the receipt oi dial impulses. i

' When relay 293 releases after all of the rst train impulses incoming to relay 201have been received, a'vcircuit' for operating the rotary stepping magnet 230 is traced liront battery through the winding o'i'rnagnet 230, right iront `contact of relay 205, back Contact of relay 293, over conductor 219 to ground at relay 202. The operation of the magnet 230 rotates thebrushes `215, 23.6, 217 and 2138 intoengagement withfthe rst set of terminals in the selected level and also opens the circuit through the winding of'relay 205. Relay 205 releases 4thereby opening the circuit through the vwinding oi the magnet 230; and magnet 230 releases. The first-set or" terminals are now tested to determi-ne 'whether they are idle or f-busy; *the i desired connection.

The levelsof the toll selector banks which represent assigned groups of telephone numbers may test circuit is traced `from battery through the @back contactsof release magnet 240, upper contact of the VON springs, winding of relay 205, back contact of rotary magnet 230, through the inner lower .back contact of .relay 212, and through the sleeve or test brush 217 to the test terminal of the engaged set of terminals. terminals is idle, the test terminal is not connected to ground and relay 212 isoperated in a circuit` from` battery through the back contact of release magnet 240, upper contact `of 'the VON springs, winding of relay 205, back Contact of rotary stepping magnet` 230, windingof relay 212,

over conductor 219 to ground at relay 202; "being, marginaL relay 205 does not operateY in thiscirt cuit. Ifthe rst set of terminals is busy, the winding of relay 212 is short circuited by the busy ground potential on the test terminal, which potential is effective` to reoperate relay 205; The ro tary stepping magnet 230 is thus reoperate'd to advance the brushes to thenext set ofvterminals.

Reoperation `of relay `205 and magnet 230 con.

tinues as long as the test brush .217 encounters busy-potential, but as soon as an idle set citerrninals is reached,relay 212 operates as above de,- sc'ribed. Relay 212, operated, connects the ground on` conductor'219, through its inner lower front contact, and through test brush`217 to thetest terminal to prevent selection of. the trunk con nected to these terminals by anyother hunting selector vhaving access'theretoi- The busy ground is also eiiective` as a holding `potentialconnected through brush 217 andl terminal` 223 to hold the succeeding switches employed in establishing-the connect to intermediate toll selectors `which in turn have access to groups of toll connectors.` In the drawings, however, the terminals 231, 232,

V233 and 234 are shown connected directly to the` toll connector. TC,` intermediate selectors being omitted. The terminals 221, 222, 223 and 224 repV resent a level of the toll `selector bank in which the terminals are connected' to 'intercepting trunk circuits,the corresponding'digit being one which represente an `unassigned group of sub scribers numbers. j

Assume, rst, `that the call from the toll operators position in Fig. 1g is extended over runk Tand toll selector TS to theftoll connector TC, the brushes of selector TS having been advanced into engagement with terminals 231, 232, 233 and 234. With relay 212 operated, a circuit is closed for operating theline relay 301 of connectorTC; this circuit is traced from battery through the lower winding of relay 301, lowermost back con- A tact of relay 306, terininal1232 and brush 216 of' selector TS, middle'lower front Contact ofrel'ay 212, lower `front contact of relay 231, innerlower back contact of relay 203, right'lower winding of repeating coil `250, resistance 253, upper front Contact of relay 204, upper right winding of repeating coil 250, upper back contact of relay`208,

upper front contact of relay212, brush 215`and terminal 231, uppermost back contact of relay 306, and through the upper winding of relay (3011 to ground. Relay 301 closes an obvious circuit for operating the release relay 302. Relay 302flocl s through" its inner upper front contact,'the inner upper back Contact of relay 304, conductor 31%1,

`inner lower backlcontact of relay 336,1conductor 313, terminal 233 and brush 217, inner lower front contact of lrelay 212, over conductor 219 to ground at relay 202. 'This ground is further extended Ii the rst set of from conductor 314 through terminal 234 and brush. 218,` the lowermost front contactof relay 212, and throughfthe lower front contact of relay 2011` to holdrelay 204 operated.

When the `toll operator dials the next digit of the called subscribers number, relay 201 `of selector TS alternately releases and reoperates causingthe corresponding release and reoperation of relay v301 of connector TC, once for each l dial impulse. The first release of ,relay 301 closes a` circuit from ground at the inner upper back contact of relay303, back contactof relay' 301,

innerlower front contact of relay 302, normally,

closed contacts Vofv the vertical oil-normal springs VON, winding of relay 303, and throughthe wind.-

ing of the vertical stepping magnet 320` to battery, The magnet 320 operates therebyadvancf.

ing `the brushes 317, 318 and 319 up to the `lirst level of the'` terminal bank. Relay 303 also fop'- crates `and as soon as the switch moves outof its normal position the circuit for energizing the windings `of magnet 3,20 `and relay 1303 is traced through the front contact of relay 303 and the .upper front contact of the` VON springsinstead of` through the normally closed Contact `of the VON springs. Themagnet 320 releases when `relay 331 reoperates at the end of. the rst impulse,

eaeh'vadditional impulse causing the reoperation and release of magnet 32,0 to advance the connector switch brushes to the level corresponding tothedgitdialed. Relay 303 is slow in releasing and remains operated until all of the impulses ofthe kseries have been received. Relay 302 is also slow in releasing and'remains operated dur` 'A ing receipt of dial impulses. y 1

When theV and last digit of` the called number is dialedgthe rst release ofrelayA 301 closes acircuit from ground at the innerupper back contact offrelay 3.33, back contact of relay 331, inner lower front contacter relay 302, upper front'contact of the VON springs, backco'ntact of relay-303,;winding or relay 305, `and through the winding of the rotary stepping magnet 330 1 to battery. The' eration ci" relay 305 connects the winding oi test relay 304 to the sleevebrushli). Themagnet 330 releases when relay 301 reoperates atV the end of the rst impulse, eachadditional impulse causing the reoperation'and release of 'magnet 330 to advance the brushes into engagement with operation of magnet 330 ad-` vances the brushes 317,318 and 319 to the first `set of terminals in the selected level and the. op`

the set ci terminals Vcorresponding to the digiti i dialed.` Relay 305 is slow in releasingv and re`- r'mainsoperated until all `of the impulses .of the series havebeen received.V Reiay 304, being somewhat slow in *operating7 does not4 operate if the Vbrush 319 engages a grounded test terminal during the advance of thebrushcs; but as soon as the brushes come to rest on theselectefd set of terminals, relay 30e operates in case the called line is buey as indicated by the grcund'potentialon the. test terminal.`

Assuming that the called'line is the line 330i` `connecting stationC of the switch when selected, the release` of relay 305 closes a to terminals 331', 332 and presence of` a f TC and that this line is `idle i circuit from battery throughthe winding of the.'V

cut-oiT relay 331 of line .333, through termnial 333 and brush 319,` lower, back contact of relay 305, inner lower back contact ofrelay 304, Umiddie upper back roiit Contact of relay302, through the upper winding ofrelay 306 to the holding ground from i. relay 202 of selector TS on4 sleeve' conductor 313;l

contact of relay 306, middlegupper i JLU thereby causing the release oi relay 20er of the toll selector TS. The release `oi relay 20e closesr Y a circuit irombattery at the baci: contact of release'magnet 240, lower iront contacts of the VGN springs, winding of relay 205, to ground at the lowerrnost Yback contact of relay 204. Relay 206'operates, thereby reversing the current over trunl; 120,V the tip conductor of trunk 120 being connected through the upper left winding of` rem peating coil 250, the upper iront contact of relay 206, resistance 251, uppermost back contact of re- Vlay 211, upper winding of relay 201, to battery at the back contact of release magnet 2410; and the ring conductor of trunk 120 is connected through the lower left inding o1 repeating coil inner lower front Contact of relay resistance 252. inner lower back contact of `relay 211, through the lower winding of relay 201 to ground. vThis reversal of current isv effective toy operate the polarized relay 11e or"` the trunl: circuit Tand a polarized'relay (not shown) in the Vtoll operators position equipment, thereby causing the dial 103 to be disconnected from the cord CCI. The operation of relay 114 closesan obvious circuit'for operating relay 1 13. Relay 113 looks under control or relay 111 and the connection from the line conductors oi cord CO1 isextended through the front contacts of rela's 112 and 113 to the leithand windings o repeating coil 118. The inner end of the lower letehand winding'of coil 11S is further connected through the winding oi relay 117 to ground, this relay being under control oi the ringing keyv (not shown) o1" the cord circuit. Withrelay 113V operated, the supervisory relay 115 and right-hand windings o1 repeating coil V118are bridged across the conductors oi trunk 120 leadingto thetoll selector TS in the distant step-by-step oiice, thereby .operating relay 115 or" trunk circuit T and maintaining the energizationof the line relay 201 or the tool selector TS. The operation of relay 115 connects the upper winding of relaylll in parallel with the "lower winding, thus reducing the resistance ci the sleeve circuit of the cord CCl suiliciently to light the supervisoryl lamp 104.

The afcrirernentioriedv operation o relay 300 o the `toll connector TC also ycauses the release o relay 301 but relay 302 is held operated through its upper winding and inner upper .iront contact, inner upper backcontact of relay 304, contro conductor 311, terminal 234 andV brush 218, the lowerrnost front contact ofv relay 212, inner lower back Contact of relay'20e, outer lower back con- Y.tact of relay 211, outer front contact ci relay 210,

outer lower back contact of relay 208, over conductor 219 to ground at release relay 202.

Further operation now awaits the operation of the ringing key at the toll operators position in response to which relay 117 of trunk circuit T is operated. Relay 11'?r connects the alternating ringing current source 119 across the outgoing conductors 4of trunkf120, thereby causing the operationoi relay v207 of the toll selector TS. Relay 207 closes a circuit for operating relayr 208. The operation of relay 203 disconnects the holder front contact of relay 211.

ing rground on conductor 219 from brush 218, thereby causing the'release of relay 302 of the connector TC. The operation of relay208 also causes the release of Lrelay 210 andthe release of relay 210ireconnects the ground on conductorV 219 to the brush 218; relay 210 is slow in releasing to insure the release of relay 302 of the connector. The release of relay 302 closes a ringing` circuit from the source ot ringing current 325, iniddle lower iront Contact of relay 300, lower winding and outer lower back Contact of relay 302, outer lower back Contact of relay 304, brush 318 and terminal 332, over line 380 and through the ringer (not shown) at station C, back through terminal 331 and brush '317, outer up` per back contacts of relays 304 and 302, to ground at they middle .upper front contactof relay 306. When the ringing key at the toll oplll erators position is released relays 207 and 208 release andrelay 210 reoperates. When the subscriber at station Crernoves `the receiver to answer the call, relay 302 isoperated by the current through its lower winding and this relay is again locked through its upper winding and inner upper iront contact over the control conductor 314 to ground at relay 2020i the toll selector TS.

Talking current is now supplied to the called sub- Y soriber in` a circuit .from battery throughthe lowern'iost front contact yof relay 206 of the toll selector TS, lower winding of supervisory relayY 213, middle lower back contact of relay 20e, lower'right winding of repeating coil 250, inner lower bachA contact of relay 208, lower front contact oi relay 201, middle lower front contact Vof relayV 212, brush 216 and terminal 232, lowermost iront contacts of relays 305 and 302 of connector TC, lowerrnost baclrcontaot of relay 3041, brush 313 and terminal 332, over line 380 and through the subscribers telephone at station C, back through terminalV 331 and Vbrush 317, the uppermost back contact o1 relay 304, the uppermost'front conf.

tacts of relays 302 and 300, through terminal 231 and brush 215, upper front contact of relay 212 of selector TS, upper back contacter' relay 208, upper right winding of repeating coil 250, upper back contact of relay 2011, and through the upper winding of supervisory relay 213 operates to effect the operation or relay 211. Relay 211 disconnects the windings of relay 201 from the left windings of repeating coil 25,0 thereby causing theV release of relay 115 or" the trunk circuit T. With relay 115 released the circuit through the upper winding of relay 111 is opened thus causing the -supervisory lamp 104 to be extinguished. The Voice currents are now Vtransmitted through repeating coils 118'and 250, Athe trunk 120 having no direct current ilowing thereover. Relay 201 ofthe toll selector is held operated by connecting resistance 214 in series with its windings, this conrelay 213 to` ground. The

nection being made at the next-to-the inner lowlays 111, 112 and 113 release, thus restoring trunk circuit T t0 normal. The release of relay 113 opens the bridge across trunk 120` causing the 202 causes the release of relays selector TS and the release of relays 302 `and 306 Yof the connector TC. The release of relay 202 Alays 202 `and 201 tov .to be restored tonornial in the tact ofrelay 302, back ."ground at the inner-upper back contact or" relay `306. Magnet 340 operateslcausing the shaft andY the locking circuit through the winding of relay 304, back Contact of Jthe i continuity through its inner upper front ner upper front contact of relay 304 to the hold` TS.v The release of relay 204 "through the lowermost terminal 232 and brushf216 of middle lower front contact of relay 212, lower front contactofrelay l,`rniddle'` of relay 208,1rightlower windi u ilower back contact "Y f ingpf repeating coil 250,'middle lower4 back cony Y 1,5913@ release of relay 201 oflthe selectorIS followed by the release of` relay 202. The release of relay 210 and 212` of closes a circuit frombattery through the middle front contact of the VON springs, winding of re lease magnet 240, through back contactsof reground. Magnet 240 opshaft and brushes ofswitch TS usual manner and release of` relay 206. When the shaft reaches normal the VON` springs are restored to erates causing the causing the normal,` releasing magnet 240.

` The release of relays 302 and 306 of connector TC closes a `circuitlfrom battery through the winding of release magnet 340, .lower front contact of the `VON springs, inner lower back concontact of relay 301, to

brushes of switch TC to be restored to normal. When the shaft reaches normal the VON springs are restored to normal releasing magnet 340.

Should the called line380 be busy when seized by the switch TC as hereinbefore described, the operation of test relay 304 disconnects the Atip and ring conductors of theconnectorfrom the brushes 317 and 313 to prevent interference with the call already in progress over the called line.' .Whenl relay 305 releases,a'locking circuit forrelay 304 is closed before theoperating circuit 'is opened, being traced from,I battery springs ofrelay'305, inner lower front contact lof vrelay 304, middle upper back contact oflrelay 306, middle upper front contact ofrelay1302, upper winding ofrelayf306, to the holding .ground from selector TS on conductorl 313. Relay 306 is sumciently energized to 4close its inner lower Vfront contact thus locking'through its lower `winding tothe ground on conductor3l3. The` operation of relay` 306 connects ground through its inner upper front contact to the in-g ner lowerarmature of relay 304 to hold relay 304.- With relay304 operated, relay 302 holds contact; and the inythe left-hand windings of repeatingcoil 118 to the Vcord `CCl and to bridge the winding of Vrelay 115 across the conductors of trunk 120 ashere- -iinbefore described. With relay 204 of the `toll selector TS released a circuit is closed fromground through interrupter 315 ofthe front contacts Lof 'relays 304, 302 and 306, thel toll selector TS,

tact of relay 204,'lower winding of relay 213, and

through the lowermost `front contact of relay 206V tobattery. The alternate closing and opening of .i this circuit under control ofV interrupter4 315 i causes `the alternate `operation and release-of relays "21s and 211.

i oi the connector l TC causing ITI.

K cause the disconnection of dial relay 115 across the operates relay 114 4oil? relay 355 overfthe toll connector TC,

ternately opens andcloses the connectionfrom battery and ground through the windings of relay 201fto the conductors of trunkl 120to` cause the alternate release and reoperation of relay, 115

of `trunk circuit and theilashing of lamp `104 'to indicatenthat the called line is lousy.V ,Whenrthe toll operator removes plug 103 fromjack 110, the` trunk circuit T, toll selector TS andconnector TC are restored to normal in the same manner as hereinbefore.. described, the release of relay 306 Assume, next that the call lfrom the toll oper ators position in Fig. `l is extended over trunk "I` andv though toll selector TS to the intercepting trunk circuit Tl in 223 and 224. Since relay V204 requires a `loclnng circuit through its lower front `contact and brush 218 in order to remain oper-1A ated `after relay 2124 operates and since the vtrunk `ITl has no conductor connected to-terminal 224 withwhich brush 218is in contact,rthe aforemen- 4' relay 212 causesl the release. relay204 released, relay 206A tioned operation of offrelay 204; ith operates as hereinbeiore described thereby connecting battery through the lowerm-ost front con-` tact of :relay 206, lower winding of relay 213,'middleilower back contact of relay 204,loWer right windingv'of the repeating coil 250,.inner lower back contact of relay 208, lower frontcontact of the release of relay;

Fig. 3a, the `brushes of switch.l TS having been advanced into engagement with relay 201, middle lower front contact of jrelay. l

brush 216 andr terminal 222 to the ring conductor 352 of trunk lTland connecting ground throughthe upper'winding of relay 2l3,`upper` back- -contact of relay 204, upper right winding of repeating. coil V208, upper front contact of relay 212, brush 215 250, upper back contact of relay and terminal 221 to the tip conductor 351 of trunk to reverse the .currentover trunk 120. and thus 105, the extension of the line conductors of repeating coil 113,V the lighting `of supervisory :lamp 104, andthe connection'of thewinding `of conductors 'of trunk 120, all

of cord CC1 to the windings Y ,1.540 The operation of relay 2061s also effective Y.

as hereinbefore described. Further operationof Y the dial's ineffective andfthelighting `of lampv completion of dialing indicates that the call is being intercepted andthe ringing.

104` prior to the key willnot be oper`ated.`

Y Upon seizure of is `closediromthe nec'ted to thetest terminal 223,V over-.test conthe trunk circuit acircuit i. busy and holding'ground con-y,V f L ductor`350,through the lower back contact of rel-, lay 355 of trunk circuit VITl and through the -s j winding Vof-trunlr` relay 354 to battery. Relay 3 54 operates l"thereby connecting; the winding of cut-r l sleeve conductorl 353 ofV trunk ITl to test terminals inthe lbanksor the` trunk iinders which have access touthis trunk.

ITll are connected-to oneof*Y the terminal banks of nder sleeve'conductor'353 is connected to ground through the 355, theupper front contact of-relay354, over thegroup conductor upper backcontact of relay".l r 70 700, through the Winding ofV group relay `'701 to'battery. rGroup relay 701opterminais '111 and. 712i` TFandthe Vthe corre-11,; Aspending testfjterminal `713 inthe test bank of nder TF. Relay 354 also closes a circuit from erates thereby connecting Yground through .its ,i

right iront contact, over conductor`l` '702,` to theV correspondingsegment of the Vertical commu-` vertical commutator `brush 717is alsol stepped tators of allY of the trunkvnders having access .to the group of trunkswhich includes the trunk ITl. In the drawings this is shown as the second segment of commutator 703 corresponding to the. second level oi the bank of switch TF.

I Assuming the trunknder TF tobe'the first idle trunk finder in the group, the operation of relay 7.01 also closes a circuit for operating relay 705.; -this circuit is from ground at the left front contact of relay 701, over the start conductor 70.4,Ythrough the inner upper back Contact of relowerrnost 'front Contact of relay 705. Relay 707:

operates thereby closing a circuit from battery at 'the uppermost back contact of relay 708, winding of the, vertical stepping magnet 720, lowermost back contact of relay 709, iront contact of 's relay707 to ground at the lowerrncst front contact of relay 705. The magnet 720 operates, thereby stepping Vthe twoy sets o brushes 761, 762191,11dj 7.63 and 764, 765and 766 up to the rst level of terminals inthe associated. banks.V The upto make contact with the iirst segment of the commutator 7.03. The operation of magnet 720 alsoy causes the release of relay 707; andthe re-Yl lease of'j'relay 707 causes the release of magnet 720;

`lrlthough,the calling trunk may be connected to terminals in the banksassociated withl brushes 761', 7 62jand. 763 or to. terminals in the banks associated with brushes 764, 765 and 766, the intercmepting trunksv ITl, IT2, ITB, 1T4 and IT5 are all' shown connectedto terminals in the sec-Vy ond' level of thev banks with which'the brushes 761; 76,27, and 763 are associated and description l ofthe terminal hunting operating of the trunk nder will, therefore,V be limited tothe ease where the Vcalling trunk is encounteredby the,

latter set of brushes. Since the trunk,l for which the' trunl; finder TF is seeking, is connected to;

terminals inv the. secondv level, the commu-tator Ybrush` 7'17; doesnot encounter vground potential on-Athe firstV cornmutator segment to stop vfurther hunting. With magnet 720 released, relay 708 reoperates again closing the circuit for operating magnet" 72,0. The'brushes are thus stepped'up to the secondllevel of thejterminal banks. Since trunk IT1 is connected-to terminals in the second level; acircuitis closed for energizing relay 709 as soon as the commutator brush 717 comes in contact with the second commutator segment;

this circuit istracedffrorn battery through the uppermost, back contact ofv relay 708, upper windn ring of, relay 707, backv contact of magnet 730, upperA winding of relay 709, commutator brush`V 717secondxcommutator segment, conductor 702 toground at the right iront contact of grouprelay-v 701. This circuit is also veiective to hold relay 707 operated; Relay 709 is' slow in operating to ensure proper positioning `of the brushes before-therst rotarystep. Relay 709 opens the circuit through the winding of magnet720vsothat magnet 720 releases. Relay, 709 alsocloses a circuit, for operating the rotaryv steppingV magnet1730,v from battery through the winding of magnet ,730, lowerrnost iront` contact of relay team i o 709, front contact of relay 707 to ground at theV lowerrnost iront contact of relay 7,05. The opere ation ofmagnet 7 30vsteps thetwofsets of brushes' into contact with the first set of terminals in the second levelA of each ot the associated banks. The circuit through the upper windings of relays 707 and 709 is opened whenY magnet 730 oper-l ates and is also opened'at the connnutator due to brush 717 being rotated out-or" alignment with the segments. Relay 707 releases but relay 709 is held operated in a circuitirombattery,through Y the uppermost back Contact of relay 708, winding of magnet720, lower winding and innerlower front contact of relay 709, to ground at the lowV ermost front contact of relay 705,; the Vcurrent in this circuit isvnot suicient to operate the mag-V net .720. if the first. set of; terminals in the second level is not the set to which the calling trunk Tl is connected, magnet 730 releases when rev lay 707 releases; relay A707 Yreoperateswhen magnet 730 releases an'd'causes the reoperation of magnet 730 to` advance the brushes into engagement with the second set of terminals. The alf ternate reoperation and release of relay 707 and rotary stepping magnet. 730 continues untilY the rtest brush 763 encounters test-terminal 713 to which conductor 353 isk connected; at which time a circuit is closed'iroin battery through the winding of the cut-01T relay 355 of trunk circuit 1'11, lower front contact of relay 354, conductor 353, terminal 71.3, brush 763, lower winding or relay `710, lowerrnost backcontact of relay 708, lower winding of relay 707 to ground at the inner lower front contact of relay 705. Relay 707 is held energized, and relay 710'is operatediin this circuit sumciently to close its inner upper front contact. Relay 710 is thusully energized and locked operatedY the circuit fron-r. battery through its upper winding and inner upper front contact, conductor 774, irontcon-tact of magnet 730, front contact oiY relay 707, to ground at the lowerrnost front Contact Voi relay 705. Magnet 7301s held operated under control of relays 709 and707. The cut-o relayr355 of trunk circuit Tl is also operated byclosure of the above Vcir-- cuit through brush 763 and terminal 713, thereby disconnecting the ground at the upper baci; contact of relay'355 from'group conductor 700. The

operation of relay 355 also causes the release of .relay 354, thereby'extending the holding ground at the upperv front Contact of relay 202 of tolll selector TS, over conductors 219 and 350, throughk the inner front contact of; relay 355-andinne1f back contact of relay 354,' to holdV relay 355 and from conductor 350-throughthe outer front conf tact of relay 355 andthe lowermost backv Contact theconnection from the toll operators position,

, over conductors 351 'and 352 of trunk ITl through terminals 711 and 712v and brushes 761 and 762,

outer back contacts of relay 706, outer front contacts of relay 710overvr conductors 771 andV 772 Y orv thetrunknder TF te lthe outgoing trunk circuit OT. Relay Y710 also closes a circuit from battery 'through the lower winding offrelay 708, middle upper front contact of relay 710, over conductorg770 to ground at the lower kiront contact Y of` the vertical off -normal springs VON; the VON springs were operated when the shaft and brushes -of relay 354i` to sleeve conductor 3 ,53tohold the trunk lnder its operated position. The l aforementioned operation of relay710 extends '60 stepped up to the iirst level; l'The operation of .relay 70,8, causes the release of relay 705fand extendsthe holding ground on sleeve conductor 353 (troni the Vv,toll selector TS) through terminal TF, lowerrnostfront contact'of relay 710, lowerv 216 of toll selector TS,

. e f 119913176 713 and brush 783, through the innerlower front contact or relay 710, the inner lowerback contactof relay 706, and the lowerrncst iront contact of relay708 to the sleeve conductor 773 leading to the outgoing trunk circuit OT. This holding ground is further'ostcnded-irom conductor 773, through the inner lower iront 708, over conductor 7741, Vto hold relay 708Moperated. `Relay 708 .also disconnects the battery at its uppermost back contact from `the'windings of relay 707 and magnet 720 and short circuits the lower winding of relay 707 thereby causing the release of relays 707 and`709. The group relay 701 releases when relay `355 of the trunk circuit ITl releases unless another trunk in the saine group is awaiting connection to another outgoing trunk, in which case the ground at the left front contact of relay 701 is extended Overloon-- ductor 704., through the outer upper front con-l tact oi relay 708, over conductor 769 to the next trunk nder (not shown) in the rotary magnet 730releases when relay 709 releases leaving only relays 708 and` 710 operated during the further extension of the connection to the intercepting operator.

With conductors 351` trunkITleXtended over conductors 771 and 772 to the outgoing trunk circuit OT, and with re lays 204 and 208 oi the toll selector TS norznal, relay 802 of the outgoing trunk circuitOT is operated in a ycircuit from groundat the lowerv back contact of relay 810, resistance 806,` lower wind ing of relay 802, ring conductor 772 of trunk finder most back contact of relayY 706, brush"762`and terminal I712 `of trunkiinder TF, conductor 352 of intercepting` trunk ITl, terminal 222 and brush Y middle lower front contact ofrelay'2l2, lower. front contact of relay 201,

inner lower back contact of relay 208, rightlower back i winding of repeating coil 250, iniddle lower contact of relay 204, lower winding of relay 213, lowerrnost front` contact Theresistance 806 ishigh enough to prevent the operation of relay 213 in this circuit. Relay 802` closes a locking circuit from battery throughits upper winding, outer lower back contacter relay 826, upper back contact `of relay 810, to ground at the inner iront contact of relay 802. The operation of relay 802 connects ground through its 819 fand closes an obvious circuit foroperating relay 807.`

outer` front 4 contact to sleeve `conductor Relay 807 closes a circuit for `operating relay 808, relay 808 closes'a circuit forV operating relay` V809, and relay 809 closes a circuit for operating relay 810. Ground at the `fro-nt contact of relay 809 is connected through i the lowerrnost front contact or relay 810 to the sleeve conductor 819.VV

With relay810 operated, the `direct current cir cuit through the lower winding of relay802 and resistance 806 is opened,rthe lower winding of relay 802 and condenser 804 in series being bridged across conductors 771 and 772; and conductor 772 is 'further extended through the lower back 3 contact of relay 825, the middle lower iront contact ofrelay 810, the lower front contact of relay 808, and throughresistance820 to ground. The Vresistance 820 is low enoughY to cause the operation of the tripping relay of a toll orlocal connector in the usual manner on calls intercepted at the banks of `such switches. The release of relay 802` causes the release of relay 807 and the release of relay 807 causes the release of relay 808. `Relay 808 :is slow in releasing 'to insure the lowresist'ance 820 being connected to 1 contact of relay and 352 of intercepting or` relay 206, to battery.

conductor 772 long "enough `togoperate the tripp ing relay'on'calls which are being received from a connector. Before resistance 820 is disconnected, a circuit is closed through both windings of the supervisory relay 213 ofthe toll selector TS and through the supervisory relay 812 of the` outgoing trunk .circuit` OT. This circuit is traced from battery through the lowermost rontcontact of relay 208, lower windingof relay 1213,1nid'dle lowerback contact of relay 204, right lower winding of repeating coil 250, inner lower backcontact of relay 208, lower front contact of relay `201, middle lower front 212; brush 216 and terminal 222, conductor 352 of trunk ITI, terminal 712 and brush` 762 of trunk nnderv TF, lowermost back contact of relay` 706, lowerrnost iront contact of relay 710, conductor 772, lower back Contact of relay 825, middlellower' front contact of relay810, back` contactyof the continuity springs orelay808, induction Acoil 816,

winding of `polarized relay 811i, windings of supervisory relay 812, upper back contact o'rrelay 825, conductor 771,' uppermostront .contact-of relay 710," uppermost back 4contactofA relay 706, brush 78liand terminal711 of iinder TF, conductor 351 of trunk IT1, terminal 221` and'brush 215 ofiseflector TS, upper front contact back contact of relay 208, -rightupperwinding of repeating coil 250, upperback Contact of relay 1 204,` 'upper winding of relay 213to` ground. The',

resistance of the lower winding `of relay 812 Vof contact of relay of 'relay 212, upper trunk circuit @Tris high enough toprevent the operation of relay 2180i" selector TS. Relay 812 operates and the polarized relay,811 also operates on an intercepted toll call, the the operating direction."Y `Relay 811 lclosesa cire` cuit1 for Yoperating relay1814. -Relay 812 closes a holding. circuit :forrelay 809( and closes a'circuit for operating relay 813.

relay 8141, to the conductors of` trunk: 900 thereby operating relay 901 of the incoming trunk cir-Y cuit IT in the oiiice `at which the intercepting` operators positions are located the winding `of V.relay 901 in series with resistance 902 being conwith the answering jack 903 and closes a circuit l through. the upper winding of relay 904. Relay 90e 4operates causing the operation ofrelay 905. f

Relay 905 connects the upper conductorci trunk V900 throughits front contact and through fcon` denser 908 to the source of ringing current 907, Ythereby transmitting an audible ringing signal i over thetrunk and through condenser 82lto oo nductor 817 of the outgoing trunk circuit OT and ',thence'back to the calling subscriber or operator.

When an interceptingoperatorinserts the plug of an answering cord in jack'903 to answer the call, and assuming the cord CC2 to be the one. used, a circuit is closed frombattery-tliroutgh` the upper back contact of relay 959, winding of relay 952, lower back Contact of relay 955, ring concurrent being in- `Relay 813 connects bat-,2 tery and ground through the windings of relay 815 front contacts of* relay 813, back contacts of 1' ductor of plug951 and jack 903, to ground at the y back' Contact' of relay 906. Relay 952 operates, closing :a circuit for operating relay 953 from battery throu'ghthe lower back Contact of re lay .959,winding and continuity back contact of relay 953, to ground at the front` Contact of` relayv 952. Relay 953 operates thereby closing a lock-` ing circuit through its continuity 'front contact,

'inner lower front Contact of relay 953,

through; the sleeve conductors of plug 951 and jack 909-, and through the winding ofrelay 90oto ground". Relay 90oy operates in this circuit thereby causing the release of relay 901 by opening the bridgeacross the conductors or" trunk 900.l With relay 906 operated, the ring conductor ofjack 903 is 'disconnected from ground and oonnectf-:dv through the front contact ofrelay 906 andlower front contact of` relay 490a to the lower. winding of relay 904. The release of relay 901- extinguishers the lamp 902 and deen- Y ergizes the Vupper winding ofrelay y904. Relay 904 remains operated temporarily, its lower winding being energized in a circuit traced through the' lower front contacts of relays 90e and 906, over the ring conductor of jack 903 and plug 951, lower back Contact of vrelay 955, resistance 965, to ground at the upper baci; contact of relay 955. ,With relay 9531op'erated,relays 95a and 955` are operatedv successivelyythe operation of relay 955 being electivezto cause the release of relays 904 and 952".` Relay 904 is held operate-d until the ground isf. disconnected from the ring V'conductor of the :gccrd to prevent false operation of relay 815 due to., adiierence in ground potential between oices. The release of relay 904 causes the release l so per windingv circuit OT, upper front contact or relay 813, lower front Contact. of relay 814, lower conductor of of relay: 905, and with relay 955 operated, a oircuit is now traced frombattery through the upoi relay 815 of the outgoing trunk trunkY 900, Vback contact ot relay 1` of Jrhe incoming rtrunk circuit 1T, iront contactof relay a 906, ring conductors of jack 903 and plug 951,

lower 'iront Contact or" relay 955, lower baclrlcontactoi` flashing key 961, windings of relays 958 andV 957, induction coil 952, over-'the tip conductors of'plug 951 and jack 903, upper back contact or" relay 905, upper conductor of, trunk 900, upper iront contact of relay 814, lower front contact of relay' 813, through the lower winding of relay 815 to gropnd'.V Relays 957l and 953 are both operatedin this circuit', the current being inthe operating direction for polarized relay 958 due to the operation of relay 8111` on an intercepted toll call. Relay 958 closes a circuit or operating relay 956 Ywhich locks under control of relay 953. The operationof relay prevents VtheoperationY of relay959 and short cirouits'the -windings of relays 957 and 958v causing the re' lease of these tworelays and: causing the operation of the'rnarginal relay 815l in the outgoing trunk circuit GT. The operation of relay 815 shortecircuits the high resistance lower winding ofrelay 812 thereby causing theoperation of the marginal supervisory lrelay 213 ofthe toll selector TS.v When relay 213 operates, it closes a circuit for operating'relay 211', therebyy disconnecting theV vwinding of relay 201 from` the conductors ci 201 operated by" lease relay 2021 off the `toll selector' TS'` and also from"J they fronti'contacty of relay 809. Should it a holdingr ground be-` Ybe necessary for the intercepting operator to-` attract the tolloperators attention, the flashing key of cord circuitv C'C2Vis alternately operated and released, thereoy intermittently opening the bridge across theV cord.V The resulting alternate release and reoperation of relay 815 causes the short circuit around the lower winding of relay 812 to be intermittently opened, thereby causing the alternate release andreoperation of relay 213 of ythe toll selectorTS; Relay 211 is thus alternately released and reoperated to cause theV alternate Voperation and release 0f relay 115l in the trunk. circuit T which results in the nashingA of theA supervisory larnp 104iof Vthe cord circuit CCl. f i 'l Upon removal of the relay 111 releases thereby causing the release of relays i12-and 113. lThe release of relay 113 opens the bridge across the conductors of trunk l but further release ol the connection is under control the intercepting operator. No'disconneet signalis given to the intercepting operator and the plug 951 should be removed frornthe answering jack as soon as it is no longer necessary to hold the connection. When the plug 951 of cord C62 is removed from jack 903, relay 953 of plug 1,03 from jaar 11o,

the cord circuit and relay 906 of trunk circuit IT Y release. The release of relay 953 causes the release of relay 956 and the successiverelease of relays 954 and 955 thus restoring cord circuit CO2 to normal; Relay 900 reconnects the winding of relay 901 in series with'resistance902 across theV conductors or trunk VY900 thereby causing therrelease of marginal relay 015 Vor the outgoing trunk circuit OT. [The release ofrelay 815 opens the shortcircuit around the high resistan'cewinding ofV relay 812 to cause the release of the supervisory relay 213 of the toll selector TS. The releaseV or relay 213 is followed by the successive release of relays 211, 201 and 202. Withj'rel'ays 201 andv 202 normal, the release magnet 2%001 selec,-

tor TS operates and the selector is restored toV normal in the Vusual manner. Upon disengagenientv of the brushes of selector TS Vand ter# ininals 221,222; 223 and-224, relayy 21201 the toll' selector releases as dc also relays `311 and 812 ot the outgoingY trunk circuit OT. `The release or"- relay 811 causes the'releasefof relay 81e and the release ofrelay 812=causes the release of relays8'1'3 and.

009; 'The release cijrelay 809 causes the release. or relay S10 and disconnects the holdingA ground from sleeve conductor 819 to' cause the release of relay 355 of the intercepting trunlr'cira` Vcuit Tl and the' release of relay'Zl'O' of the trunk. finder TF'. Y Y

lylienl relay 710 of the trunlri finder TF releases, a circuit is 'closed from battery through the winding or contact oi the VON springs, inner upper back Contact of relay '109, upper back contact of relay `710, baclr contact of relay '705, to ground` at the lower front contact or the VVGN springs. The

release magnet 740 is thus operated to return the trunk inder to normal. l/henf the shaft of the switch reaches normal, the circuitsY through the winding or the release magnet 740 and thelower windiwT or relay 'lodare opened. 1i.' the start release magnet 7610, upperrfront conductorr 70a is free from ground potentiahl when' the circuit through thelower winding o1 relay '700 is opened', or as soon thereafter as conductor 704 is free from ground potential, re-` lay 700 releases. All ci the various circuit units involved in extending a call intercepted at the bank ofatoll-selectortoan operator at a central-` nects ground through its lower intercepting switchboa hundred line cycle.

lower Winding oi relay 802 `is trac-ed above and'` the alternating current path is traced .through i nected to conductor 772 as hereinbefore `the tripping relay 302 oi connector I'Coperates sgroup` of Vline finders one of which d have now been restored to normal.

Should the called linenumber be an unassignedV partially assigned group' of oner the connection iscomnumber in a numbers,

pleted by the operation of the toll selector TS and toll ccnnectorTC, the terminals correspondi ying to ,theunassigned numbers being `connected `to one or more intercepting trunks.

` Such `a trunk is shown connected to terminals 321, 322 and 323 in the bank of switchTC, the associated trunk circuit 1T2 Ashownin Fig. 8b `being similar to the .trunk circuit'ITl of Fig. 3d.` The trunk IT2 connects toterminals 721, 722 trunk nder-'IF'and the further extension` lof 'the connection to an intercepting operators position `iscompleted in a, similarmanner to that hereinbefore described for the call intercepted 3by trunk IT1 except that relay 802 responds to either `alternating current from the source vof ringing `curfent `of connector TC cr'tofdirect current during the .silent `interval of the ringing The Vdirect current path` through the the lower winding ofrelay 802 and condenser `804 `to ground at the lower` back contact'of'relay 810. When `resistance 820 is' temporarily coridescribed,

to completethe supervisoryfcircuit between the toll selector TS andthe outgoing trunk OT. The supervisory; operations aresimilar to those on a call intercepted. over` trunk I'l, the connector TC being released when thetoll-selector TSre-` "leases in the usual` andwell known manner.` 1 Consider next a cali originated bythe subscriber at station A in Fig. 4. 'The telephoneset at station A maybe of in an'automatic telephone system, the dial 400 being provided for dialing the number of any subscribers sired. usual line circuit (not shown) fin1r the lcentral `cnice and also toy terminals in the banks` ofa designated LF is represented by the brushes` 402 and the .associated terminals. i This line'inder may' also be `of the `well,known Strowger type. For a `dis-- closure ofsuch ander anda description of its operation, reference may be had tothe patent to` H. Hovlandllo. 1,711,682 `granted May V7, 1929.

,Assume the line 401 to have been extended throughthe brushes 402 of linefinderLF tozthe line relay 403 of the associated rstselector LS. Relay 405A operates` closing an ,obvious `circuit 'for operating the release relay 404. `Relay 404`consleeve conductor 413 to` hold the line finderlli in its operated position and to hold the cut-off relay V(not shown) `of the line 401-infthe well known manner. `The dialing of the theV subscriber` at station causes the alternate release and reoperationof .relay 403 in response to the dialirnpulses lease ofrelay through the w thus created. The irst re- 403..c`loses acircuit from ground uppermost back contact of relay 405, back contact of relay 403, the upperffront 'co te .ct of relay`404, `winding `of relay 405, and lfm. net 420 tobattery.` The relay 5 and magnet 420 operatethe operation of the `magnet causing the shaitand brushes ofswitch LSV to be stepped up to the rst level ofthe terminal bank.` The reopeiation of relay 403 at thegen'dof the iirst` pulses.`

andV 723 ofr Y `ductor 409, and the vvto ground on sleeve conductor 413.

' springs, back contact of magnet 430,"

any type Suitable for useV vtor 409thence 'throught-theylowermostback conline with `which connection is de- The line 401 connects station Ato the front 1 contact i to first digit' by V fh the winding ofthe verticallstepping inagl 405 is :slow in' releasing andremains operated until all of the impulses in-thetrainhave been remains operated duringthe receipt o'f'dial im` Each succeeding release and reoperation oiY are eiiective `to cause a `corresponding operation When the shaft of switch LS is moved outof its normal position upon receipt of the iirst dial impulse, the vertical ofi-normal springs `VON are actuated and with relay404 operated as above closed from'battery throughV -thewinding lor relay described, acircuit is 407, f upper Contact of `the VON springs, iront contact of relay 405, vtothe holdingv ground `on conductor"413.VRelay 407 closes a locking circuit Vtraced Afrom the upper Vcontact ofthe VONlsprings, through the bank Contact of the rotary stepping magnet 430,con-

outer front contact fof relay 407 to ground atthe uppermost back contactof relay 406.0Whenrelay 405 releases after all of 'relay 403 response to dialimpulses impulse causes therelease of magnet '420. fRelay received.` Relay 404 isfalso slow in releasingrand 1 of magnet 420, the brushes"417,418` and 4,194 being thereby stepped up to the responding tov the digit dialed.

the impulses corresponding to the rst digit have been received, a circuit is closed from battery `through the winding of `magnet 430, inner front contact of `relay 407, back'contact of relay 405, Theorem tionof magnet 430 advances the brushes ofswitch LS into ContactV with the rstset `of terminals in theselected level andopen's the circuit Vthrough Vthe winding ofxrelay 407. The releaseof relay 407 causeslthe release of magnet 430. The release" of magnet 430 connects the` winding of relay 407, throughthe upper contact of the VON to conductact of relay 406 to sleeve A'brush'419 and also of the 11th relay 407. Re-

Vfrom .conductor 409 through the winding of relay y 406. andthe V.lower back contact rotary. step springs to the holding ground on conductor 41,3. `Ifthe iirst set of contacts 'is idle,

` rela'y406 operates in series with v145 Y lay 407 is marginalfanddoes notfoperateunless l therst set of terminals is busy, inwhich case thejbrush 419 vencounters ground potential on the terminal with 'which it is; in Contact, the. Winding yof relay 406` beingsliortcircuited. i With irelay 407 reoperated, `the rotary steppingf'magnet V430 y reoper'ates thereby advancing the brushes of switch LS Vto theneXt setof terminals inthe selected i level. Relay 407 and magnet 430 thus continue` their cycle of operations as above `described to advance the brushes `of switch LS until an idle 'set 'of terminals is encountered at which time relay 406 `operates to extend the connection from line 401 through itsy inner front` contactsj to f brushes 417and 418. With relay'406` operated.4

the sleeve conductor 413 is connected'through i thelowermost front contact of relay 406 to sleeve brush 419. The operation of relay 406 also causes,

the release of relays 403 and-404. Relay 404 be-` ing slow in releasing maintains the holding ground 'on conductor413 until a holding ground has been supplied through brush 419 from the succeeding switch or trunk as afresult of its seizure as hereinafter described. Relay 406` is thus 'held oper-.- ated, after relay` 404 releases, `by the holding groundsupplied through brush 419.

The levels of the localselector 'banks'which represent assigned groups of ltelephone numbers` -may connect to intermediate selectors which ini.7s

turn/have access'to groups of localconnectors.

are. shown connected directly Ato the; local con# vhector LlCoi Figi... 'The terminals .421, 422V and,

423e` represent a level or'theI first selector bank .in ,which they terminals are l connected to intercepting trunk circuits, the 'corresponding digit being one which represents an unassigned group oisubscribers numbers.

-Assuming rst that thecall is for an assigned Vnumber and. that; brushes 417, 418 and 419 have been advanced. into `engageinent with terminals 431.; 432 and 433, tlneconnection` from ,line 401 is extended throughbrushes 417 and 418 and terminals 431 and 432, and through the inner 'back-contacts of relay 5040i connector LC to i the windings Yof line relay 501.

,Relay1501 opcrates;` in turn-causing the operation oi relay 502.

Relay 5.02 connects groundthrough its lower front `contact oversleeve' conductor 513 vto test terminal 4'4B-3fmholclirelayelli. of the; selectorSl and also tohold the line iinder in its operated position 1 vand/tohold the. cut-ofi relay (not shown) of the line '401. all in. the well known manner. When the calling subscriber dials'the, penultimate digitofthe called subscribers number, relay 501is all ternately released-and reoperated in responsev to the dial impulses thus created. The rst release of relay 50,1 closes a circuit from ground at its 'backicontacu through the inner upper front con- -tact of relay 502, normally closed contact of the Y Vertical off-normal springs VON, winding or Vre,-

lay503 andA hrough the winding of the vertical vstepping magnetV 520 to battery. Therelay 503 and magneti520 bothoperate, the Yoperation of the-magnet stepping the shaft and brushesrof switch LC up toY the first vlevel. ofl the terminal bank.r When relayir50l reoperates, magnet 520 releases, butvrelay 503 is slow in releasingand remains operated untilall of the impulses in theV Y. y4() .L

Y A vin releasing and remainsoperated until the con*v train have been received.` Relay 502 is also slow nection is' released by the calling. subscriber.

lsponding to the advanced from its normal position 'in response to the rst impulserthe circuit for holdinglrelay- 503 and Vreoperating magnet 520 Ais traoedthrough Each Succeeding release of relay501 causes the L.reoperation `of magnet 520 thereby advancing the brushes5rl7, 518 and 510V up tothe level cor-ree digit dialed. :After the switch is the :upper front contac'tjof the vertical ofnormal springs VVON'and'the front contact of relay 503Y iinstead of through the normally closed contact Voi the. VON springs.

, Vlil/'hen relay 501 releasesinresponse to the first impulse/created.'bythe dialing of the last digit of the called subscribers number, relay 505 and the rotary stepping magnet 530r are operated in Y Y a `circuit Virornbatteryv through the winding' of Y contact of relay 505being in parallel with the upmagnet 530 and outer upper back contact of relay 5,11'in parallelrwith'battery through the winding of relay-505, through the upper back contact'of relay 507, back contacter relay 503, upperofrontV contact ,of the VOlXlsprings, inner upperiront contacter. relay 5702, to groundV at the back contact of relay 501.` rllhe Voperation of relay 505 renders the energizat'ion of this relay andinagnet 530'ndependent of relay 507, the upper front per back Contact of relay 507. The operation lof v.magnet 530 advances the brushes 517, 518 and 519 into contact withthe firstset of vtermina-ls in the selectedv level. The reoperationrof relay 501 atfthef end of the rst 'impulse causes the release or magnet `530..V g Each succeeding release orV relayY 50:1 causesr the reoperation ofV magnet Inniganawever, 'the' terminals 431.1432 and 433 f 53o,l 'thereby the windings of relay currents` being transmitted through condensersV 500.

advancing the" brushes' of .switch LC into engagement with the set of terminals connected to the .line "of Vthe called subscriber. Relay 505 is slow in releasing and remains operated-until all oi? the impulses have been received.

Before relay 505 releases, a busy test circuiti.Y is:A

traced from battery through the windingo'f relay 50.7., inner upper back contact of relay 511,1 lower 519 to the `sleeve terminal of the selected line. if 'the' line ifsvbusy relay 507 operates due to 1i relayj507 operates, it remains operated kafter vrelay 505'releases the holding circuit being traced through the inner back contact of relay 505 and the outer front contact of relay 50'7- over 'conducitor 513,to groundat the lower iront contact of .relay 502.Y A busy tone is transmitted tothe calling station by connecting theV left-hand winding of the tone .source 512 through'the'inner front" contact of relay 50'? toY the lower one of talking condensers 500. f i

v Assuming that the oalled'line is the line 580 connecting the station B to the terminals 541,

542'and 543v and that this line is idle,'the release i 'ront contact of relay 505, through sleeveorush f lo v r *Y there being a busy-ground .potential on this termi-nal.

cuit from battery through its upperiwindingand inner upper front contact over conductor 514 to ground at the uppermost'front contact oi relay 502 isxeiectiv'e to complete the operation ofrelay 511. With relay' 511` operated, groundv Vis connected throughlitsnext to the outer lowerI front contact tosleeve brush 519 asa line busycondition. With/relay 511 operated, a signaling'circuit is closed from the ringingcurrentvsource 525, 'through the inner lower 'front contact of relay 511,:lower winding andV lower back contact of f relay 506,lower1nost front contact of relayA 511, brush 518, terminal'542, over, the line580 Vand throughV theV ringer (.not'shown) V at station B,

most front Contact of relay 511, to ground at the upper back contact or" relay 506. When the sub-Y back through terminal 541 and brush 517, upperscriber at station B removes thev receiver, relay Y 506 is energized sufficiently by the current through its lower winding to operate its innerupper `iront contact thereby closing va circuit' from-batteryA through its upper winding and inner Y,upper front 4contactto ground on conductor ,514.' 'Ihevoperation of relay 506 connects a sourceo talking curi ,rentV to-Y the line 580; battery is connected.

through thev upper winding of 'relay 504 and up- 0 perrnost front contacts of relays 506 511 to brush 517 and ground is connected ,through the vlower winding of relay 504` and lowerrnost front contacts of lrelays 506 and 511 to brush 51S; With the" receiver Vremoved from the receiver hook atstation B relay 504 is operated thereby reversing the connections between the; windings oi relay 501 and the line conductors incoming to` the connector LC. The current'is thus reversed over the calling'line circuit to indicate that the called subscriber has answered the c all. Talking current isfurnished to the calling station through 501, the voice frequency When theconnection is'released by the `subscriberat station A, `relay 501 releases andwhen i the receiver is replaced at station B relay 504 `releases. The release of relay 501 Icauses the release of relay 502. Relays 506 and 511 are held.

until relay 502 and 504 are bothrreleased." With relays 501, 502 and 511 normal, a circuitisclosed from battery through the windingv `of release magnet 540, lower contact of the VON springs, lower Vback contact ofA relay `511,and upperback contacts of relays 502 and 501` to ground.` The operation of magnet 540 causes the switch toirestore to normal in the usual manner. When the shaft and brushes reach normal position, the circuit through the winding of magnet 540 is opened `atthe VON springs.

VUpon releaseof `relay`502, as above described, the holding ground isi disconnected from conductor 513 therebycausingV the release of relay 406 ofthe selectorLS and the release of the line nder LF and therelease of the cut-off relay -1 (not shown) ofA line 401,;the line finder LF being restoredto normal in theusual manner.` The' release` of relay 406 closes a circuit from battery through the winding of releasemagnet 440,lower Contact of the VON springs 'and upper Ybaclr con- `tactswof relays 404, 402 and 406 to ground`. The

operation-of magnet 440 causes the switch LS to restore to normalin the Vusual manner. 1 When the shaft and brushes reach normal position, the

circuit through r'the winding of magnet 4401s 'opened at the VON springs.

f Ifthe selector LS is advanced toa level of the terminaljbank which represents an unassigned j group of subscribers numbers, the call is extend; ed to an intercepting operator, the terminals in this level being connected to oneV or more intercepting trunks. Thus the terminals 42,1, 422 and 423 inthe bank of selector LS are shown ,connected to the `intercepting` trunk ITS` in Fig.

5a. Since the localselectors have no means for` signaling over a selected trunk, as do the connectors and tollselectors, the trunk ITB is ar` ranged to respond to its seizure to initiatetlie `further extension of the connection totheinteri cepting yoperator and to` hold the selector and line linder switches in their operated positions.V Upon seizure of trunk ITS, the calling line loop n, is extended through brushes 417 and 418, terminals 421 and 422, and through the back contacis` of relay 558 to thewindings of line relay 551. The operation of relay 551 causes the `successive `operation or` relays 552,553 and 554.

'The operation of relay 553 connects ground through its outer lower front contact over sleeve conductor 569 to sleeve termina-1 423 to hold re-` lay v406 of selector LS and to held the line nder LF and cut-off relay (not shown) of line 401 in Ythe usual manner. The trunk `ITS isY shown connected to terminals 731, 732 and 733 in the bank of vtrunk nder TF and is shown as beingj in thesame group of trunks as are'the trunks ITl Vand IT2; having the common grouprelay 701.

The operation of relay 553 connects. ground lthroughits inner lower front jcontact, the lower back contact of relayA 555 and `the uppermost back Contact of relay 557 `to conductor 700` thereby operating thepgr'oup relay 701.. The operation` of relay 554 connects battery throughlthe winding of the cut-off relay 555 Vin parallel with resistance `559 through theupper front contact .of relay 554 and the innerupper'back contact of relay V557 to the sleeve conductor 563 connected to terminal 733V in the bank of nder TF?.

The trunknnder TF, orv a similar nderhaving (terminal 733 and brush 763, lower iront contactof relay 710', inner lowerb'ack "access to ltrunk ITS, is thereupon operated in the manner hereinbefore` described to step `its lbrushes upto the level in which.` the terminals of trunk ITB are located and to rotate its brushes into engagement'with these terminals.; When' brushes 761, 762 'and 763l engage the'` terminals 731, 732 and'733,the cut-oli relay-555is connected through brush 763, the lower vwinding of relay 710, loweriback contact of relay 708, lower winding oi relay 707, to ground at the inner lower front cont-actor `relay 705. The finder switch TF is thus stopped on the terminals in question and extends the connection fromtrunk II3 l to the outgoing trunk circuit OT. The operaticn of relay 555 connects the sourceof ringing current 560 vthrough the lower front contact of relay 555 `and through condenser 567 toone of the incoming line conductors thereby transmitting a ringing tone to the calling subscriber. Relay 555 also disconnects the ground at relay 553 from group conductor 700.

'120 The operation of relay 555closes a circuit from battery through w the winding of relay 556, through the upper front vcontact of relay 555,and the lower back contact of lrelay 557, conductor 562, lthrough terminal 732 and brush '7.62 conductor 772 of the outgoing` trunk circuit OT, lower winding of Vrelay 802, and throughresistancei806 to ground at the lower back contact of relay810.1-R'elay 802- operates but relay 556 is marginal anddoeswnot` operate in this'circuit. The operation` of` relay S02 causes Vthefurther` extension of the intercepted call through trunk circuit 'OT out over trunk 900 to 4the incoming trunk-circuit IT at the intercepting operators position inthe man'- vner hereinbcfcre" described. When relay 810 operates the tripping resistance 820 is connected to conductor 772 as hereinbeforev described .to

"cause the operation of l relay 556..:Relay-v 556 4locksthrou'gh its inner upper front contact and resistance 564, over sleeve conductor 563, through through the inner contact of relay/706, outer lower front Contact of relay.708,`sleeve conductor `773 of trunk-finder TF, and over sleeve conductor 819 of the outgoing trunk circuit OT, lowermos't front ContactV `of relay 810, to ground at `thefront `contactzof f relay 809. `The operation ofrelay 556 also causes Y the operation of relay 557. Relay 557 locks under control of relay 554, and causes the release of the cut-oil relay 555. to disconnect .the audible Y ringing tone. Withrelays 556 and 557'operated,

a` supervisory circuit is closed "from 'battery through the upperiwinding of relay 553 of trunk V,IT3,.outer upper front contacts of relays 553 -and556, over conductor 561,"through terminal 731 and brush '761i of trunk-lnder TF. uppermost back-contact of relay 706,"uppermost front contact of relay 710, conductor 771, upperback contactiof relay 325 of the outgoingYV trunk circuit OT, windings of relay 812, winding of relay 811, induction coil 816, back contact of re1ay`808,

.middle lower front contact of relay 810, lower of the lower. windingof `relay 812; Irelay 811 Y being polarized does ,not operatebecause` the currentls not in theoperating direction. Since 

